The present invention is directed generally to methods of recycling used or scrap polymers and more particularly to recovering a polyester or a polyvinyl chloride layer from a multilayered scrap or waste material in a form suitable for reprocessing into useful articles.
The supply of natural resources has been dwindling and, at the same time, the use of synthetic materials has increased dramatically. Known supplies of raw materials such as petroleum are being rapidly consumed in the manufacture of polymers. Rapid, efficient, safe and relatively low cost methods of recycling scrap or waste polymer into new and useful articles would reduce the requirement for raw materials and thus preserve natural resources.
One major source of scrap or waste polyester is discarded liquid containers such as those used by the liquid beverage industry. Empty beverage containers are generally discarded, too often along public roadways or in public parks. Tremendous quantities of polyester could be salvaged and recycled from these containers. However, since polyester allows gas molecules to pass, the containers are generally lined with a thin layer of polyvinylidene chloride. The polyester must be separated before it can be reprocessed.
Another important source of scrap or waste polyester is photographic or X-ray film. Such film generally consists of three main layers: a polyester base or sheet for toughness and strength; an intermediate layer of polyvinylidene chloride; and an upper layer of gelatin containing a silver halide. However, scrap or waste film may also contain polyvinyl chloride or be contaminated with cellulose acetate. Silver recovery processes generally remove only the silver bearing gelatin layer.
Substantially all of the known prior art polyester recovering methods involve the use of one or more organic solvents such as tetrahydrofuran. Many of these organic solvents are inherently dangerous, are an explosion or fire hazard, harmful to workers' health, and remain in, and adversely affect the environment.
It is a primary object of this invention to recover polymers such as polyester or polyvinyl chloride from multilayered scrap or waste materials by a rapid, efficient, safe, and relatively low cost process.